NHC/Copper-Cocatalyzed [4 + 3] Annulations of Salicylaldehydes with Aziridines for the Synthesis of 1,4-Benzoxazepinones.

N-heterocyclic carbene/copper-cocatalyzed [4 + 3] annulation of salicylaldehydes with aziridines was developed, giving the corresponding 1,4-benzoxazepinones in good yields with exclusive regioselectivity. Copper serves as a Lewis acid to activate the small strained aziridines, and the formation of NHC-salicylaldehyde adduct plays an important role in improving the regioselectivity.